The present invention relates to electro-optic devices and, more particularly, to electro-optic devices having enclosed therein at least one photovoltaic device.
Heretofore, devices of reversibly variable transmittance to electromagnetic radiation have been proposed for such applications as the variable transmittance element in variable transmittance light-filters, variable transmittance eyeglasses, variable reflectance mirrors; and display devices which employ such light-filters or mirrors in conveying information. These variable transmittance light filters have included windows. Among such devices are those where the transmittance is varied by thermochromic, photochromic, or electro-optic (e.g., liquid crystal, dipolar suspension, electrophoretic, electrochromic, etc.) means and where the variable transmittance characteristic affects electromagnetic radiation that is at least partly in the visible spectrum (wavelengths from about 3800 xc3x85 to about 7600 xc3x85). Typically, proposed control schemes for variable transmittance windows either allow the windows to be power controlled window-by-window with a person determining when the window should darken or have all windows controlled by a central computerized power source such that the window is darkened when the sun shines on them or on a sensor placed on a particular side of a building.
Devices of reversibly variable transmittance to electromagnetic radiation, wherein the transmittance is altered by electrochromic means are described, for example, by Chang, xe2x80x9cElectrochromic and Electrochemichromic Materials and Phenomena,xe2x80x9d in Non-emissive Electrooptic Displays, A. Kmetz and K. von Willisen, eds. Plenum Press, New York, N.Y., pp. 155-196 (1976) and in various parts of Eletrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCH Publishers, Inc., New York, N.Y. (1995). Numerous electrochromic devices are known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741; Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecak et al., U.S. Pat. No. 4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos. 3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos. 3,282,157, 3,282,158, 3,282,160 and 3,283,656.
In addition to these devices there are commercially available electro-optic devices and associated circuitry, such as those disclosed in U.S. Pat. No. 4,902,108, entitled xe2x80x9cSingle-Compartment, Self-Erasing, Solution-Phase Electro-optic Devices Solutions for Use Therein, and Uses Thereofxe2x80x9d, issued Feb. 20, 1990 to H. J. Byker; Canadian Patent No. 1,300,945, entitled xe2x80x9cAutomatic Rearview Mirror System for Automotive Vehiclesxe2x80x9d, issued May 5, 1992 to J. H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled xe2x80x9cVariable Reflectance Motor Vehicle Mirrorxe2x80x9d, issued Jul. 7, 1992 to H. J. Byker; U.S. Pat. No. 5,202,787, entitled xe2x80x9cElectro-Optic Devicexe2x80x9d, issued Apr. 13, 1993 to H. J. Byker et al.; U.S. Pat. No. 5,204,778, entitled xe2x80x9cControl System For Automatic Rearview Mirrorsxe2x80x9d, issued Apr. 20, 1993 to J. H. Bechtel; U.S. Pat. No. 5,278,693, entitled xe2x80x9cTinted Solution-Phase Electrochromic Mirrorsxe2x80x9d, issued Jan. 11, 1994 to D. A. Theiste et al.; U.S. Pat. No. 5,280,380, entitled xe2x80x9cUV-Stabilized Compositions and Methodsxe2x80x9d, issued Jan. 18, 1994 to H. J. Byker; U.S. Pat. No. 5,282,077, entitled xe2x80x9cVariable Reflectance Mirrorxe2x80x9d, issued Jan. 25, 1994 to H. J. Byker; U.S. Pat. No. 5,282,077, entitled xe2x80x9cVariable Reflectance Mirrorxe2x80x9d, issued Jan. 25, 1994 to H. J. Byker; U.S. Pat. No. 5,294,376, entitled xe2x80x9cBipyridinium Salt Solutionsxe2x80x9d, issued Mar. 15, 1994 to H. J. Byker; U.S. Pat. No. 5,336,448, entitled xe2x80x9cElectrochromic Devices with Bipyridinium Salt Solutionsxe2x80x9d, issued Aug. 9, 1994 to H. J. Byker; U.S. Pat. No. 5,434,407, entitled xe2x80x9cAutomatic Rearview Mirror Incorporating Light Pipexe2x80x9d, issued Jan. 18, 1995 to F. T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled xe2x80x9cOutside Automatic Rearview Mirror for Automotive Vehiclesxe2x80x9d, issued Sep. 5, 1995 to W. L. Tonar; and U.S. Pat. No. 5,451,822, entitled xe2x80x9cElectronic Control Systemxe2x80x9d, issued Sep. 19, 1995 to J. H. Bechtel et al. Each of these patents is commonly assigned with the present invention and the disclosures of each, including the references contained therein, are hereby incorporated herein in their entirety by reference.
Photoelectrochromism is discussed generally in pages 192-197 of Electrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCH Publishers, Inc., New York, N.Y. (1995). Specifically, section 12.2.3, entitled xe2x80x9cCells Containing Photovoltaic Materialsxe2x80x9d, discusses how a photovoltaic material produces a potential when illuminated and where the photovoltaic material has an internal rectifying field which provides a driving force for the electrons. This section goes on to describe that the voltage created by the photovoltaic material is insufficient, by itself, to darken the electrochromic material. Therefore the electrochromic cell incorporating a photovoltaic material needs an external bias applied which is supplemented by the small photovoltaic-voltage to cause electron transfer to proceed, i.e., have the electrochromic material darken.
Heretofore, various other electrochromic devices have been devised wherein the transmission of light therethrough or reflected thereby automatically varies as a function of light impinging thereon. For example: U.S. Pat. No. 5,377,037, entitled xe2x80x9cElectrochromic-Photovoltaic Film for Light-Sensitive control of Optical Transmittancexe2x80x9d to H. M. Branz et al. teaches a variable transmittance optical component which includes a solar cell-type photovoltaic device. The photovoltaic material is deposited over the entire surface of a transparent electrically conductive layer section. The photovoltaic material includes a p-type hydrogenated silicon carbide section, an undoped hydrogenated silicon carbide section, and phosphorous-doped hydrogenated silicon carbide section. A standard solid-state electrochromic multilayer structure is then deposited over the layer of photovoltaic material such that the light traveling through the optical transmitter must travel through the photovoltaic material and through the electrochromic material. The photovoltaic material will absorb some portion of the light and will also create sufficient current to darken the electrochromic material. Solid-state electrochromic devices with good memory, once darkened, will not clear or bleach quickly without an external method of closing the electrochemical circuit, i.e., the device will not clear in a reasonable time even though the xe2x80x9cdarkening potentialxe2x80x9d is removed. The device taught by Branz et al. attempts to overcome this significant limitation by connecting a bleeder resistor to the two transparent conductive electrode layers to provide the electric potential and circuit across the device (to slowly bleach the device). In operation, the photovoltaic device produces a DC current which is applied between the transparent conductive layers and across the bleeder resistor. However, it takes a light source with the intensity of 1-2 suns to produce a transmission drop of only 10 percent, in approximately 12-13 minutes. Thus, incorporating a bleeder resistor complicates the circuitry required for the window system and also draws some power that otherwise could be used in darkening.
U.S. Pat. No. 5,348,653, entitled xe2x80x9cStand-Alone Photovoltaic (PV) Powered Electrochromic Windowxe2x80x9d to D. K. Benson et al. teaches a variable transmittance double pane window including a five-layer solid state electrochromic portion, an array of photovoltaic cells with a n-type conductivity region on the front side of a p-type silicon substrate, and an external switch-containing circuit. The photovoltaic cells are deposited directly on the glass and not on the transparent electrode. The photovoltaic cells and the battery circuit are connected in parallel to the electrochromic portion of the device. This allows selective activation of the electrochromic portion to either a substantially opaque state or a substantially transparent state by switching the external switch-containing circuit between having the photovoltaic devices drive the device to a dark state, or to a transparent state or having the battery device drive the device to a transparent state when the conditions are such that the incident sunlight is not sufficient for the photovoltaic array to produce the required energy. Again, solid-state electrochromic devices with good memory, once darkened, will not clear in a reasonable amount of time absent some method of closing the circuit, typically by applying a bleaching potential.
U.S. Pat. No. 5,457,564, entitled xe2x80x9cComplementary Surface Confined Polymer Electrochromic Materials, Systems, and Methods of Fabrication Thereforexe2x80x9d to Leventis et al. teaches an electrochromic device having polypyrrole-prussian blue composite material on the oxidatively coloring electrode and a heteroaromatic substance with at least one quaternized nitrogen on the reductively coloring electrode. Preferably, either the oxidative or reductive polymer is electro-deposited onto a metallic oxide to increase the cycle life of the device to an acceptable level. Leventis et al. also teaches using an external photovoltaic cell to generate power to darken the electrochromic device. The photovoltaic cells operate as forward biased diodes and allow current to flow in the opposite or xe2x80x9creversexe2x80x9d direction. Further, Leventis et al. places the photovoltaic cells behind the electrochromic device such that the light which drives them must first travel through the electrochromic material. As the degree of colorization of the device increases, the intensity of light impinging on the photovoltaic cells decreases and the output from the photovoltaic cells decreases, creating a limit of how much light the device can block.
When retrofitting electro-optic devices in the configuration of windows it is disadvantageous to have to run wires to each window to supply the external bias. Furthermore, even when installing electrochromic windows into a new building it would be easier and less expensive if no wires were needed to supply an external bias or no external circuits were necessary to help control colorization or bleaching of the window. Consequently, it is desirable to provide an improved electro-optic device having an improved photovoltaic drive mechanism.
Accordingly, a primary object of the present invention is to provide an improved electro-optic device having a discrete photovoltaic device integrally combined with the electro-optic device where no external drive voltage is needed, no bleaching circuit is required, and no external wiring is necessary.
Another object of the present invention is to overcome disadvantages in prior electro-optic devices of the indicated character and to provide improved electro-optic devices wherein the transmittance of light therethrough automatically varies as a function of light impinging thereon.
Another object of the present invention is to provide improved electro-optic devices which may be in the configuration of windows and eyeglasses which darken and clear uniformly in an aesthetically pleasing manner.
Another object of the present invention is to provide improved windows and eyeglasses which incorporate improved means for adjusting the amount of light that is transmitted therethrough to a desired and comfortable level.
Another object of the present invention is to provide improved self-erasing electro-optic devices that are economical to manufacture, durable, efficient and reliable in operation.
Another object of the present invention is to provide improved electro-optic devices wherein excellent speed of light transmissive change, good uniformity of light change across the entire surface area thereof, and continually variable light transmissive characteristics are obtained throughout the range of light transmittance of the devices.
The above and other objects, which will become apparent from the specification as a whole, including the drawings, are accomplished in accordance with one embodiment of the present invention by enclosing within an electro-optic device a discrete photovoltaic assembly which is capable of driving the electro-optic medium. The electro-optic device has front and back spaced-apart glass elements sealably bonded together defining a chamber filled with an electro-optic material. The front glass element has a transparent conductive layer on the face confronting the rear glass element and the rear glass element has a transparent conductive layer on the face confronting the front glass element. The seal is generally disposed some small distance from the perimeter of three edges of both glass elements and some greater distance in from the remaining (fourth) edge. The photovoltaic assembly is placed between the two glass elements on the outer perimeter along this fourth edge with the photon-absorbing (active) side of all the photovoltaic cells within the photovoltaic assembly facing in one direction. Alternately, the photovoltaic assembly or an array of assemblies may be placed in a sealed off region or regions any place within the window area and may even be in the form of a decorative design, such as a diamond, circle, and the like, and may assist in providing and maintaining the spacing between the transparent conductor-coated glass elements. The photovoltaic assembly is electrically connected to the two transparent conductive layers and when light impinges on the photovoltaic cell an electrical potential is generated which darkens the electro-optic material in proportion to the amount or intensity of impinging light. By choosing the relative area of the photovoltaic assembly to produce the correct current for the electro-optically active window area, the amount of darkening of the electro-optic portion can be directly and accurately controlled without the need for any circuit, wires or shorting resistors.
In addition, an apparatus for making an electro-optic window having two members capable of securing and holding two glass elements in a spaced-apart and parallel relationship is provided. The glass elements may be secured by vacuum-applying members or simple clips. The glass elements may be held in a spaced-apart and parallel relationship by a hydraulic mechanism or by simple spacers placed between the securing members.
In accordance with another embodiment of the present invention, electrochromic eyeglasses are provided wherein the transmission of light therethrough automatically varies as a function of light impinging thereon. Eyeglasses embodying the present invention include left and right lenses which are integrally mechanically and electrically connected together as a unitary structure. The lenses have front and rear spaced glass or plastic lens elements with a chamber disposed therebetween, the front and rear lens elements being transparent. One side of the front element confronting the rear element includes transparent electrically conductive means, and one side of the rear element confronting the front element also includes transparent electrically conductive means. The chamber disposed between the front and rear elements contains an electrochromic reversibly variable transmittance medium in contact with the transparent electrically conductive means on the front and rear elements. A photovoltaic cell is provided for applying electrical potential to the electrochromic medium to cause variations in the light transmittance of the electrochromic medium, the photovoltaic cell being disposed between the right and left lens portions of the eyeglasses. The photovoltaic cell is electrically connected to the two transparent electrically conductive layers so that when light impinges on the photovoltaic cell an electrical potential is generated which causes the electrochromic material to darken in proportion to the amount or intensity of light impinging thereon. By controlling the relative area of the photovoltaic assembly to produce the desired electrical current for the electro-optically active lens area, the amount of darkening of the electrochromic material may be directly and accurately controlled without the need for external electrical wiring, batteries or bleeder resistors.